Light coupling from a junction laser into a monomode fibre with a glass cylindrical lens on the fibre end

Abstract A new method of producing a small cylindrical glass lens on the end of a glass fibre is described. The intensity distribution in the focal plane of such a lens formed on the end face of a monomode fibre was measured. An improvement factor of 2.5 in the coupling efficiency into the fibre from a stripe geometry GaAs laser was observed. The tolerances of the coupling laser-fibre are carefully measured. In contrast to previous work it is shown that the improvement in coupling efficiency is obtained only at the expense of much tighter alignment tolerances.